Li+ substitution induced O3/O′3 biphasic tailoring strategies enhancing anion/cation synergetic redox of Na-rich manganese-based cathode for sodium-ion batteries

Na-rich manganese-based layered oxide cathodes have presented potential applications in high energy–density sodium-ion batteries due to their cost-effectiveness and large theoretical specific capacity. However, the low kinetics of anionic redox reaction and lattice distortion caused by the Mn 3+ Jahn-teller effect greatly hindered the actual capacity, rate, and cycling performances of these cathodes. Herein, a Li + substitution induced O3/O′3 biphasic tailoring strategy has been proposed for constructing the Na-rich NaLi 0.2 Mn 0.8 O 2 (NLMO) cathode. Compared with conventional O′3-Na 1.2 Mn 0.8 O 2 (NMO) cathode, the O3/O′3-NLMO cathode enabled to provide an ultrahigh capacity of 233 mAh g −1 , superior capacity retention of 86 % after 50 cycles, and outstanding rate performance with the recorded-up capacity of 165 mAh g −1 at a high current density of 200 mA g −1 . In addition, NLMO also displayed rapid Na + -diffusion and more structural reversibility of O3/O′3-P3-O1-P3-O3/O′3 during the entire charging and discharging processes. The above excellent performances of NLMO cathode could be attributed to the well-designed O3/O′3 biphasic structure that provides the synergistic function of drastically enhancing reaction kinetics of anionic (O − /O 2– ) couple and efficiently alleviating multiphase transitions caused by Mn 4+ /Mn 3+ cationic couple. This unique finding of Li + substitution induced biphasic structure provides an insight for developing economical and high-performance Na-rich oxide cathodes.